Finding Nemo’s clock reveals switch from nocturnal to diurnal activity

Abstract

Timing mechanisms play a key role in the biology of coral reef fish. Typically, fish larvae leave their reef after hatching, stay for a period in the open ocean before returning to the reef for settlement. During this dispersal, larvae use a time-compensated sun compass for orientation. However, the timing of settlement and how coral reef fish keep track of time via endogenous timing mechanisms is poorly understood. Here, we have studied the behavioural and genetic basis of diel rhythms in the clown anemonefish Amphiprion ocellaris. We document a behavioural shift from nocturnal larvae to diurnal adults, while juveniles show an intermediate pattern of activity which potentially indicates flexibility in the timing of settlement on a host anemone. qRTPCR analysis of six core circadian clock genes (bmal1, clocka, cry1b, per1b, per2, per3) reveals rhythmic gene expression patterns that are comparable in larvae and juveniles, and so do not reflect the corresponding activity changes. By establishing an embryonic cell line, we demonstrate that clown anemonefish possess an endogenous clock with similar properties to that of the zebrafish circadian clock. Furthermore, our study provides a first basis to study the multi-layered interaction of clocks from fish, anemones and their zooxanthellae endosymbionts.

Diversification of habenular organization and asymmetries in teleosts: Insights from the Atlantic salmon and European eel

“…We note that in our study, the presence of this additional nucleus correlates with species endowed with complex life cycles and light dependent phase transitions. During these transitions, these species go through major morphological, physiological and behavioral changes, regulated by environmental factors including photoperiod and temperature, and involving neural circuits remodeling ( Ebbesson and Braithwaite, 2012 ; Strand et al, 2018 ; Cresci et al, 2020 ; Schalm et al, 2021 ). As a major forebrain center integrating environment and complex behavioral, cognitive and emotional organismal responses, the habenulae may be involved in these modifications.…”

Long-Term Monitoring of Diel and Seasonal Rhythm of Dentex dentex at an Artificial Reef

“…A similar precaution is adopted when evaluating the ecological meaning of species peaks in catches or visual census; i.e., animals captures or spotting are provoked by their increased availability in the sampling area for their resting or because of their activity (Aguzzi and Bahamon, 2009;. Notwithstanding, many species of fishes display activity rhythms (e.g., Eriksson, 1978;Muller, 1978;Helfman, 1986) that drive changes in abundance between day and night in coastal areas, as detected by different sampling systems and methodologies (e.g., Aguzzi et al, 2013;Hawley et al, 2017;Schalm et al, 2021). Diurnal, nocturnal, and crepuscular activity is often described as a product of fish behavioral response to solar irradiance variations (Helfman, 1986;Coles, 2014).…”

Berberine Ameliorates Metabolic-Associated Fatty Liver Disease Mediated Metabolism Disorder and Redox Homeostasis by Upregulating Clock Genes: Clock and Bmal1 Expressions

“…It is known that transcriptional and post-transcriptional feedback loops involving a group of circadian proteins govern circadian rhythms. In mammals, the endogenous clock system consists of a well-characterized transcriptional and translational feedback loop (TTFL) composed of core clock gene elements: heterodimers composed of transcription factor activators (Clock and Bmal1) proteins that activate the transcription of inhibitor genes (PERs and CRYs) [ 37 ]. The transcriptional activation of circadian genes by Bmal1-Clock heterodimers can bind to the E-box of CACGTG, and this results in the expression of PERs, CRYs, and other related genes [ 38 ].…”